Recent analysis of primate dental structures indicates that the crystallographic orientation of enamel nanocrystals adapts to the mechanical demands of an organism's diet.

最近對靈長類牙齒結構的分析顯示，牙釉質奈米晶體的晶體學取向會根據生物飲食的機械需求而適應。

The structural integrity of vertebrate enamel is facilitated by hydroxyapatite nanocrystals organized into rods. While macroscale adaptations, such as enamel thickness and cusp morphology, are well-documented, the nanoscale orientation of these crystals has remained under-examined. Utilizing a novel methodology termed Polarization Enabled Large Input of Crystal Angles at the Nanoscale (PELICAN), researchers analyzed twelve specimens across nine primate species, spanning 17.8 million years of evolutionary history. The data demonstrate a positive correlation between the misorientation angle of adjacent nanocrystals and the hardness of the consumed diet. For instance, the nut-consuming Cercocebus atys exhibited significantly higher misorientation modes compared to the fruit-consuming Pan troglodytes.

脊椎動物牙釉質的結構完整性是由排列成棒狀的羥基磷灰石奈米晶體提供。雖然宏觀層面的適應（例如牙釉質厚度與牙尖形態）已有詳盡記錄，但這些晶體在奈米尺度上的取向一直缺乏研究。研究人員利用一種稱為「奈米尺度晶體角度極化啟用大輸入 (PELICAN)」的新方法，分析了九個靈長類物種的十二個樣本，跨越 1,780 萬年的進化史。數據顯示，相鄰奈米晶體的取向偏差角度與所食用飲食的硬度之間存在正相關。例如，食用堅果的 Cercocebus atys 展現出顯著高於食用果實的 Pan troglodytes 的取向偏差模式。

Within the genus Homo, this nanoscale adaptation aligns with significant dietary transitions. The introduction of meat approximately 2.0–1.5 million years ago coincided with an increase in misorientation relative to earlier hominins such as Paranthropus boisei. A further increase was observed during the transition to agriculture approximately 12,000 years before present, as evidenced by a comparison between pre-agricultural and agricultural Homo sapiens samples. Conversely, the Industrial Revolution did not precipitate a statistically significant shift in nanocrystal misorientation. These findings suggest that crystallographic misorientation serves as a mechanism to enhance enamel resilience, potentially compensating for the reduction in molar size observed throughout human evolution. The presence of low-angle grain boundaries is hypothesized to stabilize nanostructures by hindering dislocation motion, thereby increasing fracture toughness.

在人屬 (Homo) 之中，這種奈米尺度的適應與重大的飲食轉型一致。約 200 萬至 150 萬年前引入肉類飲食，與早期人類（例如 Paranthropus boisei）相比，取向偏差有所增加。在約 12,000 年前轉向農業期間，透過比較前農業時代與農業時代的 Homo sapiens 樣本，觀察到取向偏差進一步增加。相反，工業革命並未導致奈米晶體取向偏差出現統計上顯著的轉變。這些發現表明，晶體學取向偏差是一種增強牙釉質韌性的機制，可能補償了在人類進化過程中觀察到的臼齒尺寸縮小。假說認為，低角度晶界可以透過阻礙位錯運動來穩定奈米結構，從而提高斷裂韌性。

Enamel nanocrystal misorientation increases in response to more mechanically challenging diets, providing a nanoscale adaptation that complements macrostructural dental changes.

牙釉質奈米晶體取向偏差會因應更具機械挑戰性的飲食而增加，提供一種補足宏觀牙齒結構改變的奈米尺度適應。